Prepared statements, form submission, form validation and displaying errors in php

PHP Code.

Insert statement Query.

INSERT INTO `users`(`user_id`, `user_first`, `user_last`, `user_email`, `user_uid`, `user_pwd`) VALUES (1,'Adnan','Zaib','text@.com','Admin',1234)

What are Prepared statements and how to use them

//Created a sql prepare template

$sql = "SELECT * FROM users WHERE user_uid=?;";

//than send to database with certain values left(unspecified parameters).

//Create a prepared statement

$stmt = mysqli_stmt_init($conn);

 

//prepare the prepared statement

if(!mysqli_stmt_prepare($stmt, $sql)){

echo "sql statement failed";

}else{

//bind values to parameters and further to placeholder

mysqli_stmt_bind_param(#stmt, "s",);

// ‘s’ stands for datatype of parameter that you are going to pass.

}

 

while($row = mysqli_fetch_assoc($result)){

echo $row['user_uid'] . "<br>";

}

PHP form Validation 

<?php

// define variables and set to empty values

$name = $email = $gender = $comment = $website = "";

if ($_SERVER["REQUEST_METHOD"] == "POST") {

  $name = test_input($_POST["name"]);

  $email = test_input($_POST["email"]);

  $website = test_input($_POST["website"]);

  $comment = test_input($_POST["comment"]);

  $gender = test_input($_POST["gender"]);

}

 

function test_input($data) {

  $data = trim($data);

  $data = stripslashes($data);

  $data = htmlspecialchars($data);

  return $data;

}

?>

//Note: Also check notebook for php validation code.

                        PHP form Validation

            Php form validation way 2 is below.

Validate name:

$name = test_input($_POST["name"]);
if (!preg_match("/^[a-zA-Z-' ]*$/",$name)) {
  $nameErr = "Only letters and white space allowed";
}

 

Validate Email:

$email = test_input($_POST["email"]);
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
  $emailErr = "Invalid email format";
}

 

Validate gender and comment:

if (empty($_POST["comment"])) {
    $comment = "";
  } else {
    $comment = test_input($_POST["comment"]);
  }

  if (empty($_POST["gender"])) {
    $genderErr = "Gender is required";
  } else {
    $gender = test_input($_POST["gender"]);
  }

Showing errors in the php form submitting.

How to write form for showing error. Define value attribute and echo input values with e.g:value = <?php echo htmlspecialcharacters($email) ?>

When you refresh or access the form page than you will get an error message on input fields which I will give solution later on.

Input faild values will show data after the form will submit, therefore its would show error So, how to remove these error? Solution is simple, you just need to define attribute ‘named’ variables with default empty string values. Look below the fist line of code.

 

$error[‘title’] = “title must be letters and spaces only”;

Write this line according to field name in every if condition than these error will be shown to user after submitting the form.

Video resource through netninjas

 

                        Checking for error

You can also save data to database after that redirect the user to other page.